The present invention relates to a method for preparing an ink for use in, for example, ink-jet recording, an ink cartridge filled with the ink, and an ink-jet recording apparatus using the ink as a recording ink.
An ink including a coloring material (such as a dye or a pigment), a humectant and water is conventionally known as an ink for use in the ink-jet recording. When an image is formed on a recording medium such as recording paper by using the ink including the coloring material, however, the water resisting property of the image is disadvantageously low, namely, if the image gets wet with water, the coloring material oozes out into the water. In particular, when the image is recorded on ordinary paper (i.e., commercially available paper occasionally used in an electrophotographic copying machine that does not have a structure, a composition and characteristics optimum for the ink-jet recording), the water resisting property of the image is very poor.
Therefore, as described in, for example, Japanese Laid-Open Patent Publication Nos. 10-212439, 11-293167 and 11-315231, a hydrolytic silane compound (an organic silicon compound) is conventionally included in the ink so as to improve the water resisting property of an image formed on a recording medium. In the case where the silane compound is thus included in the ink, when ink drops are adhered onto a recording medium and a moisture content (solvent) is evaporated or permeated into the recording medium, a condensation polymerization reaction is caused in the silane compound remaining on the recording medium, so that the condensation-polymerized silane compound can surround the coloring material. As a result, even when an image formed on the recording medium gets wet with water, the coloring material can be prevented from oozing out into the water.
However, in such a water resistant ink including the hydrolytic silane compound, and particularly when the ink includes a water-soluble dye having a water-soluble solubilizing group of at least one of a sulfonic group and a carboxyl group, agglomeration refractory or insoluble in water may be produced through interaction between the dye and the silane compound during the preparation of the ink. Therefore, it is necessary to remove the agglomeration, which largely lowers the production efficiency of the ink. Furthermore, the agglomeration refractory or insoluble in water may be similarly produced also during storage of the ink. Therefore, the agglomeration may be produced, for example, on an ink jetting nozzle of an ink-jet head loaded with a cartridge filled with the ink, which can cause an ink-jet failure.